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TELEPHONE RECEIVER. No. 355,424. Patented Jan. 4, 1887.

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NITED ST TES PATENT OFFICE.

ERANK o. WATKINS, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR, BY

MESNE ASSIGNMENTS, To THE UNITED STATES KRO'IOPHONE ooMrANY,

OF NEWV YORK, N. Y.

TELEPHONE-RECEIVER.

SPECIFICATION forming part of Letters Patent No. 355,424, dated January 4, 1887.

Application filed April 27, 1886. Serial No. 200,371. (No model.)

To all whom it may concern: Be it known that I, FRANK C. WATKINS, citizen of the United States, residing at Philadelphia, in the. county, of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Telephone- Receivers; and I do declare the followingto be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the letters and figures of reference marked thereon, which form a part of this specification.

My invention has relation to telephone-re eeivers; and the object is to provide a simple and reliable receiver without the use of aperinanent magnet, and at the same time operate successfully in the direct or primary transmittercircuit, thus dispensing with the induction'coil in the transmitter; and to these ends the novelty consists in a receiver pro vided with an iron diaphragm and a soft-iron core surroundedby a helix of iron wire,which in turn is surrounded by a secondary helix of copper wire, as will be hereinafter more fully described, and particularly pointed ontin the claim.

In the accompanying drawings the same lotters of reference indicate the same parts of the invention.

Figure l is a longitudinal section of my improved receiver, and Fig. 2 is a modification of the same, showing a larger form of receiver adapted to long-distance signaling.

A is the mouth or earpiece, and is secured in the usual form to the body B, and G is the diaphragm of the ordinary construction.

D is the soft-iron core, which is surrounded by a helix of iron wire, terminating in the posts E E, and on the outside of the iron helix is a secondary coil of copper wire terminating in the posts .F F.

It will thus be seen that two independent circuits run through the receiver, one through the iron coil, and a second one through the copper coil. completed through the local. circuit of the transmitter, and one end of the second or copper circuit is grounded and the other runs to the line. t

The variations of the transmitter-circuit in the primary iron coil are inductively amplified in the secondary copper coil, and in this condition transmitted to the receiver at the other end of the line, and the varying intensity of the current correspondingly affects the magnetic state of the iron helix and core, so as to produce a motion of the diaphragm, and at the same time any foreign induced influence on the line is reduced to-a minimum through the interposition of the iron helix.

The circuit in the iron coil is In the modification shown in Fig. 2thesame' I constructiouis employed, exceptthat the iron core and theiron and copper helices are lengthened out to get a larger amount of wire close to the core and amplify the unagnetic action FRANK o. WATKINS.

\Vitnesses:

H. J. E NIs, J No. N. OLIVER. 

